A 32-year-old man who lives in downtown Philadelphia presents to his physician with a 4-day history of terrible headache, fever, and stiff neck. He has always been in good health and attributes this to his healthy eating habits and his daily running through the city parks near his apartment. The physician suspects the man may have cryptococcal meningitis and collects CSF for examination. Which of the following laboratory tests would best definitely diagnose cryptococcal infection in this patient?
|A||Quelling reaction capsular swelling|
|B||Latex agglutination test for polysaccharide capsular antigen|
|C||Ouchterlony test for fungal infection|
|D||India ink test for the presence of capsulated yeast|
a. is a test useful for diagnosing Streptococcus pneumoniae and uses capsule-specific antibody to cause capsule swelling;
b. is an immunodiffusion test useful in diagnosing Histoplasma and Blastomyces fungal infections;
c. India ink does provide rapid diagnosis of Cryptococcus neoformans; however, this assay is positive in only 50 percent of cryptococcal cases. Nigrosin is also used for negative stain.